This invention relates to a feed arrangement for open-end friction spinning machines of the type having two friction rollers that are arranged next to one another to form a wedge-shaped gap serving as a yarn forming region or point. The friction rollers are drivable in the same rotational direction. A feeding and opening device is also provided that has an opening roller surrounded by a housing having a discharge opening for contaminants/dirt. The arrangement also has a fiber feeding duct starting approximatley tangentially at the opening roller and leading to the wedge-shaped gap. A suction device is provided for holding the fibers and the forming yarn in the wedge-shaped gap and a yarn withdrawal device is provided for withdrawing the yarn in the longitudinal direction of the wedge-shaped gap.
In the case of the arrangement of the initally mentioned type, such as disclosed in German Published Unexamined Patent Application (DE-OS) 29 43 063, the fiber transport from the opening roller to the wedge-shaped gap is caused essentially by the vacuum generated in the area of the wedge-shaped gap. Since the wedge-shaped gap is also open at different points with respect to the atmosphere for generating the air currents required for the spinning, relatively high suction air current must be taken in requiring a high air capacity installation. This high demand for air can create problems with respect to the cost effectiveness of a machine composed of a plurality of such arrangements.
In order to improve the fiber feeding from the opening roller to the wedge-shaped gap and make it more uniform, it is also know from German Published Unexamined Patent Application (DE-OS) 28 12 471 to subject the area of the opening roller to overpressure. In order to avoid a feedback of this overpressure in the area of the fiber material to be fed, in the case of this construction, the whole feeding and opening device is subjected to overpressure. This results in considerable costs with respect to construction but also in the fact that it is no longer possible to provide a discharge opening in the area of the circumference of the opening roller through which dirt and impurities contained in the fiber material are discharged.
The invention has the objective of improving an arrangement of the initially mentioned type by providing that the volume of air required for the air currents in the area of the wedge-shaped gap can be reduced, while still maintaining a perfect, and if possible, improved fiber transport between the opening roller and the wedge-shaped gap.
This objective is achieved by connecting to the fiber feeding duct in the area of the circumference of the opening roller a compressed air duct aimed into the fiber feeding duct, and by arranging the discharge opening in the transport direction of the fibers at a distance in front of the compressed air duct.
In the case of this development, the two systems of different air currents, namely the area of the discharge opening and the area of the fiber feeding duct, are separated from one another with respect to space. The compressed air duct aimed into the fiber feeding duct causes, or at least supports, the transport of the fibers to the wedge-shaped gap so that the required capacity installed for the suction device in the area of the wedge-shaped gap can be reduced. The additional costs of construction are minimal. In particular, it is also possible to utilize the compressed air created when the vacuum flow in the area of the wedge-shaped gap is generated for the area of the compressed air duct.
In a further development of the invention, it is provided that the compressed air duct is arranged approximately tangentially with respect to the opening roller as an extension of the fiber feeding duct. The jet of compressed air flowing out of the compressed air duct will then be directed in such a way that the possibility of a feedback to the area of the discharge opening for impurities is reduced further. In order to reduce this feedback still further, it is provided in a further development of the invention that the opening roller in the area between the discharge opening and the compressed air duct is covered by a wall piece that is adapted to its contour and serves as a screen. The length of this wall piece must be adapted to the technical spinning conditions and perhaps also to the resulting varying pressure values of the compressed air of the compressed air duct which can be determined by means of simple tests. The sealing effect may also be improved by providing the wall piece with at least one longitudinal groove extending in the axial direction of the opening roller. As a result, a type of labyringth seal is created in the area of the wall piece.
In a further development of the invention, it is provided that the compressed air duct is divided into several small ducts which, with their own mouths, lead into the fiber feeding duct. As a result, the compressed air flow can be made more uniform or may also be distributed differently in a manner that is especially desirable and advantageous for the opening and the transport of the fibers.
In a further development of the invention, it is provided that the fiber feeding duct is divided into at least two partial ducts to which, in each case, its own compressed air duct is assigned. As a result, the flow in the fiber feeding duct, and thus the fiber transport, can be made more uniform and can be proportioned as desired. By selecting the pressures in the individual ducts and thus of the air currents in the individual partial ducts of the fiber feeding duct, an adaptation to varying spinning conditions can be achieved.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.